Digital counter



Jan. 15, 1963 R. R. BOCKEMUEHL ETAL DIGITAL COUNTER Filed July 30, 19592 Sheets-Sheet 1 ATURNEY Jan. 15, 1963 R. vR. BOCKEMUEHL ETAL DIGITALCOUNTER 2 Sheets-Sheet 2 Filed July 30, 1959 RNW@ nit ,t L

3,073,522 Patented Jan. l5, 1963 fte pas

3,073,522 DIGITAL COUNTER Robert R. Bockemuehl, Birmingham, and EugeneA.

Hanysz, Royal Oak, Mich., assignors to general Motors Corporation,Detroit, Mich., a corporation of Delaware Filed .inly 30, 1959, Ser. No.839,499- 11 Claims. (Cl. 23S- 20 The present invention relates toelectronic counters and, more particularly, to digitalr counterseiiective to record the net number of positive events.

Under certain circumstances it is desirable to follow the motion of'amember such as a machine tool, a rotating shaft, etc.by digitallyrecording small increments of the members movement. This can be a highlyaccurate method for following motion providing the count can beaccurately made. Heretofore, the counters available have'not beenparticularly adapted for use in such applications. In one form ofcounter the number of events are counted irrespective of their sense.Counters of this type canbe employed when the motion is always in onedirection. However, if the motion is reversible, such counters giveerroneous and misleading results. To overcome this difiiculty, countersmay be employed which will only, count events ofV one particular sense,i.e., positive or negative. By employing two counters of oppositesenses, the difference between the two counts will equal the net numberof events. However, such arrangements not only necessitate a needlessduplication of equipment, but also are not direct reading and,consequently, cannot be` employed for preset counting.

It is now proposed to provide a net positive digital counter which willbe effective to record the net number of positive events which occureven though negative events are interspersed in the series of positiveevents. More particularly, this is to be accomplished by providinganegative count storage circuit which will record the number ofconsecutive negative events and a logic circuit adapted to count thecompletion of positive events only when there were no negative eventspreviously stored in the storage circuit prior to the commencement ofthe positive event.

More particularly, this is tobe accomplished by providing one or moremulticathode, gaseous discharge tubes adapted to count positive andnegative events according to their sense and to store a count of thenegative events. If'negative counts are stored the occurrence of anadditional event will be counted according to the sense thereof'. Thus,a negativeevent will increase the negative count, whereas a positiveevent will reduce the count. In the event the negative count has beenreduced to zero, a gate circuit will be opened after the stored count iszero andthe occurrence of any further positive events will betransferred through the gate to a conventional counter mechanism.

ln the drawings:

FIGURE l is a block diagram of a net positive digital counter embodyingthepresent invention.

FIGURE 2 is a block diagram of the logic circuits employed in FlGURE 1.

FiGURE 3 is a wiring diagram of the circuit portion of FIGURE l.

Referring to the drawings in more detail, the present invention isembodied in a digital counter for registering the net number of positiveevents which occur. The counter includes a pickup 22'that is sensitiveto the occurrence of the events to be counted and is effective` toproduce a' series of electrical signalsv indicative thereof. The pickup22' is, in turn, connected to a negative count storage circuit 24 and acomplete-cycle memory circuit .26 that are effective to feed a logiccircuit 28 which, in

turn, actuates a conventional recording counter 30.

ln the present instance` the pickup 22 hasa pairof output conductors 32and 34 that areeach connected to the inputs` of the negative. countstorage circuit 24 and also the inputs of the complete-cycle memorycircuit 26. Whenever events are occurring, there will be a series ofpulses on each of the conductors 32 and 34 with a separate pulseoccurring in each conductor for each event. Although there will be anoverlapping of the related puses, thefcommencement and terminationsthereof will correspond-to the sense of the events, i.e., whether or notthey are occurring in a positive or negative direction. Moreparticularly, if a complete negative event occurs, a pulse will commencefirst in the conductor 32 and then the conductor 34. Subsequent to thecommencement of the pulse in conductor 34, the pulse in conductor 32will terminate and finally the pulse on conductor 34 will terminate.Conversely, if a complete positive event occurs, there will be a pulsein conductor 34 first, then a pulse in-conductor 32, then the pulse inconductor 34 will terminate and, finally, the pulse in conductor 32 willterminate.

The negative count storage circuit 24 contains a conventionalmulti-cathode discharge tube 36 having an anode 33, a first set of guidepins 38, a second set of guide pinsti and a plurality of outputcathodes. Although there may be any number of these cathodes, in thepresent tube 36 there are ten output cathodes numbered, consecutively,KU to K9 inclusive. These cathodes are symmetrically disposed around theanode 33 so asto be equally spaced therefrom and so as to have the guidepins 38 and 40 interspersed therebetween. Cathode K0 is connected toground by means of a load resistor 42 so that a voltage will appearacross the resistor 42 if the discharge is located on the K0 cathode.Cathode K1 is connected to a second load resistor 44 which is, in turn,connected to a reset switch 46.that grounds the resistor when it isclosed. Cathodes` K3 to K8 are connected directly to the reset switch46. Cathode K9 is not connected to anything and has a floatingpotential. As a result, it may be seen that the discharge may settle onany of the cathodes K0 to K8. However, due to the floating potential ofcathode K9, it will be irnpossible for the discharge to settle thereon.

The first set of guide pins 38 contains ten pins that are interspersedbetween the various cathodes 0 to 9 and are all connected to theconductor 32. The second set of guide pins 40 are substantiallyidentical to the first set 38 and are also interspersed between thecathodes and are connected to the conductor 34. It should be noted thateach guide pinrin one group is always disposed on the right side of itsassociated cathode, while each pin in the other group is disposed on theleftvside of its associated cathode. It may thus be seen that,whenproceeding around the tube 36 in a negative direction, there will bea cathode, a guide pin in the firstset 38, a guide pin in the second set40, a cathode etc. However,Y when proceeding in a positive direction,the order will be reversed, i.e., a cathode, a guide pin in the secondset 40, a guide pin in the first set 38, a cathode etc.

Thus, if a negative event occurs, the conductor 32 will apply a pulse tothe guide pins in the lirst set 38 whereby the glow discharge will betransferred from the output cathode upon which it is located to thenearest guide pin in the first set 38; The second conductor 34 willthensup-4 ply asecond pulse to the second set of guide pins 40.Subsequent to this, the pulse on the first set of guide pins 38 will beremoved, whereby the discharge will transfer from the guide pin in thefirstset 33 to the closest guide pin in the second set 4G. Upon thecompletion of the event this second pulse will terminate. and thedischarge will transfer to the adjacent output cathode. It may thus beseen that the occurrence of a series of negative events will cause thedischarge to be sequentially moved in a negative direction from cathodeto cathode so that a negative count corresponding to the number ofconsecutive negative events will have been stored. It should be notedthat, although there are only nine cathodes, in the present instanceseveral discharge tubes may be cascaded to permit the storage of as manynegative counts as will be required for the particular installation. Inthe embodiment illustrated, negative events transfer the discharge in adirection from K1, to K1 while positive events transfer the discharge inan opposite direction.

Whenever a positive event occurs, the pickup 22 will rst supply a pulseto the guide pins in the second set 4G, a pulse to the guide pins in thefirst set 38, remove the pulse from the second set 4G and then removethe pulse from the first set 38. As a result, a series of positiveevents will cause the discharge to be transferred in a positivedirection from cathode to cathode so as to reduce the stored negativecount by a number corresponding to the number of positive events thathave occurred. However, since the number nine cathode is disconnectedand has a floating potential, the discharge cannot be transferred beyondcathode K even though a positive event occurs when there is no negativecount previously stored. Accordingly, if the discharge is located oncathode K0 and a positive event occurs, the discharge will betransferred to the guide pins but will then return to cathode Kp. Thusthe only way for the discharge to arrive at cathode K0 is for a positiveevent to occur.

It may thus be seen that, when more than one negative count is stored,there will be no signals across either of the resistors 42 or 44.However, if a single count is stored, there Will be a square wave acrossthe resistor 44 that will commence when the discharge settles on cathodeK1 aud terminates when it leaves cathode K1. Similarly, when the storedcount is reduced to zero, there will be a square wave across theresistor 42 that will last for a period corresponding to the time thedischarge is on cathode K11. It should be noted that, since the storedcount is zero when the discharge is on cathode KU, whenever thedischarge leaves K0 an event will have started when no previous negativecounts were stored. This condition will be unambiguously indicated bythe termination of the square wave across resistor 42.

The complete-cycle memory circuit 26 includes a second multicathode,gaseous discharge tube 48 which is substantially identical to the iirstdischarge tube 36 for storing counts. However, in this tube 48 everyother cathode is connected together to form an odd set S0 that isgrounded through a load resistor 54 while the remaining cathodes areconnected together to form an even set 52 that is grounded through asecond load resistor 56. The first set of guide pins S8 is connected tothe iirst conductor 32 from the pickup and the second set of guide pins60 is connected to the second conductor 34.

It may thus be seen that, normally, the discharge will be settled on oneof the cathodes in the odd set 50 or one of the catbodes in the even set52. The location of the discharge on the odd or even set 50 or 52 willbe apparent by the voltage appearing across the odd or even resistors 54and 56 resulting from the current of the discharge.

If an event of either sense, i.e., positive or negative, begins, thepulses produced by the pickup and present on the conductors 32 and 34will be applied first to the guide pins in one or the other setdepending on the sense of the event. This will thereby cause thedischarge to be transferred from a cathode to the nearest guide pin inthe set which is energized. If the event continues to occur, a secondpulse will be applied to the guide pins forming the other set and thetirst pulse terminated. Only when the event is completed will the secondpulse be terminated. When this pulse is terminated the discharge willtransfer to the adjacent cathode. It may thus be seen that thecompletion of a positive or negative event will cause the discharge totransfer in a positive or negative direction respectively from a cathodein the odd or even set to the adjacent cathode in the other set.However, it may also be seen that, unless an entire event is completed,the discharge will not be transferred to another cathode but insteadwill remain on a guide pin or even be returned back to the originalcathode. In other words, the discharge cannot be transferred from an oddcathode to an even cathode or vice versa unless the entire event iscompleted in either a positive or negative direction.

In order to raise the outputs from the negative storage discharge tube36 and the complete cycle discharge tube 48 to more usable levels, foursubstantially identical buffer or squaring circuits 62, 64, 66 and 68are provided. In the present instance each circuit includes a pair ofinterconnected vacuum tubes 70 and 72 that are arranged so that theoutput tube 72 is conducting or non-conducting according to the presenceor absence respectively of an input signal on the grid 74 of the tube70.

The grid 74 of the input tube 70 of the first squaring circuit 62 iscapacitively coupled to the load resistor 42 by condenser 76 andresistors 78 and 80. The bias supplied through the resistor 80 to thegrid 74 will normally retain the input tube 7 0 cut-olf and the outputtube 72 conducting. As a result of the plate current, the potential onthe plate 82 will be depressed. However, when the discharge in the countstorage tube 36 settles on the cathode KD, a square wave voltage signalwill appear across the load resistor 42. This will pass through thecondenser 76 to the grid 74 and will cause the grid 74 of the input tube76 to become sufficiently positive to cause the tube 70 to conduct. Theplate current will cause an increase in the voltage drop across theplate load 84 and lower the potential on the grid 86 of the second tube72 below cut off. As a result the plate voltage will rise to B supplyvoltage for a period corresponding to the time the discharge is on thecathode K0. The output from square circuit 62 will be a square wavehaving a pulse width that is a function of the time that a signal isapplied to grid 74. This square wave is applied to a differentiating andpositive clipping circuit 128 and a negative pulse corresponding to thetrailing edge of the square wave from circuit 62 is applied to grid 126.

The second squaring circuit 64 is substantially identical to the firstcircuit except that it provides a negative pulse voltage output ascompared to the relatively positive voltage output of squaring circuit62 and it is responsive to the drop across the load resistor 44 in thecircuit of cathode K1. This change in polarity of output can beaccomplished in squaring circuit 64 by connecting the output lead to theplate of a tube that is equivalent to tube 70 in squaring circuit 62rather than to the plate of a tube that would be equivalent to tube 72.It is seen that output lead 88 is connected with the grid of tube 114through a diiferentiating and positive clipping circuit 130 which passesonly negative pulses.

The third and fourth squaring circuits 66 and 68 have negative pulseoutputs the same as squaring circuit 64 and are connected, respectively,to the load resistor 54 in the odd cathode circuit and to the loadresistor 56 in the even cathode circuit and the outputs 90 and 92thereof are connected to the plate of the input tubes the same as in thesecond squaring circuit 64. Thus, the potential of the output 96 of thethird squaring circuit 66 will be high when the potential of the output92 of the fourth squaring circuit 68 is low and vice versa. Theparticular condition, of course, will be determined by whether thedischarge is on a cathode in the even set or a cathode in the odd set.

The logic circuit 28 for actuating the counter 30 is shown in block formin FIGURE 2 and includes a rst bistable flip-flop circuit 94 having apair of inputs 96 and 98 coupled to the outputs of the first and secondsquaring acreage circuits 62 and 64, a second bistable flipiiop circuit1th)- having a. pair of inputs 162 and 194 that are capacitively coupledto the outputs of the third and fourth squaring circuits 66 and 68, adiode OR circuit 106 interconnected with the output of the secondflip-dop circuit 160, a diode AND circuit 168 interconnected with theoutput of the OR circuit 106 and with the output of the iirstisquaringcircuit 62 and also a gate circuit 11) interconnected with the output ofthe first tiip-iiop circuit 94 and triggered by the AND circuit S.

More particularly, the rirst hip-flop circuit 94 is of conventionaldesign and includes a pair of vaccum tubes 112 and 114 that have thecathodes interconnected through a common cathode biasing circuit 116 andthe plates 1181 and 120 connected to the high voltage source by separateload resistors 122 and 124. The control grid 126 of the irst tube 112 iscoupled to the output of the iirst squaring circuit 62 by means of adifferentiating and positive clipping circuit 128. The control grid 127of the second tube 114is coupled to the output of the second squaringcircuit 64 by a differentiating and positive clipping circuit 13G. Thedip-flop circuit 62, as is well known to those skilled in the art, willhave two stable states of operation. In one state of operation, the tube112 is conducting and the tube 114 is non-conductive. In the other stateof operation, the tube 114 is conducting and tube 112 is non-conducting.If' one of the differentiating circuits 12S or 130 applies a negativepulse to the grid of the conducting tube, that tube will be drivennon-conductive and the other tube conductive. Another negative pulse tothe same tube will then not change the conducting conditions of thetubes. More particularly, if the irst tube 112 is conducting and thedischarge passes across cathode K0, a square wave pulse will be appliedto the input grid 'i4V of the iirst squaring circuit 62 so as to producea positive square wave pulse at the output. This wave, in turn, will. befed to the diterentiating and positive clipper circuit 128. This circuitwill then supply a negative pulse to the grid of the input tube 112 atthe same time that the square wave terminates. This is coincident withthe discharge leaving the K0 cathode and is an unambiguous indicationthat no negative counts were stored when the event started. Thisnegative pulse will cut off' the tube 112 .and cause the plate voltageto rise to a higher positive level. Tube 112 will continue to benon-conductive until a negative pulse is applied to the grid 127 of thesecond tube 114 to cut it oit. This occurs when the discharge hitscathode K1 and causes a negative pulse in the Output of the'second4squaring circuit 64. The beginning of this negative pulse will beetective to cause a negative pulse to pass through the differentiatingandpositive clipping circuit 13t) and cut oif the second tube 114. Inorder to more fully describe the foregoing action, it is pointed outthat the output voltage from iiip-iiop 94 will be developed at the topend of resistor 136l which is connected between a negative potential andthe plate 11S of tube 112. When tube 112 is non-conducting, thepotential of the top end of resistor 136 rises sharply positive anddrops sharply when tube112 is conducting. It thus is seenthat with tube112 conducting, there is no voltage developed to attempt to turn gatetube 132 on. On the other hand, there is a voltagedevelopedto turn gatetube 132 on wheny tube 112 is non-conducting. Non-conduction of tube 114will not Cause a voltage rise to attempt to turn gate tube 132 on'.

The gating circuit 110 includes a vacuum tube 132 that has the controlgrid 134 directly connected to the plate 118 ofthe iirst tube 112. ofthe tiip-iop circuit 94 and also to a fixed` negative bias voltagesource 136; Normally, this biassource1'36will be ableto maintain thegrid 134 below cut-off bias so that the gate 110 will be closed.However, when the tirst tubey 112 in the iiip-iiop circuit 94becomesnon-conductive, the grid 134 of the tube 132 in the gate 110 willswing suiiciently'positive` to nected with circuits 142 and 144 whereasiiip-liop 94 has; only one output from plate 118. The control grid of-lthe first tube is connected to the plate of the input tube.

of the third squaring circuit66 by a differentiatingand positiveclipper' circuit 13Sthat is connected to the plate. ofthe input tube inthe third squaringcircuit 66 responsive to the voltage across the loadresistor 64 formingthe. output of the odd cathode set.

of the fourth squaring circuit 68 by a differentiating and positiveclipper circuit 140. This circuit 140'is fed from.

the plate of the input tube in the fourth squaring circuit.

68 so as to be responsive to the voltage across the resistor 56 formingthe output of the even cathode set. Thus, this flip-Hop circuit 11i@will also have two stable states,. i.e., one tube is conducting and theother tube is nonconducting or the reverse thereof depending uponwhether the discharge is located on an even cathode or an odd, cathode.However, when the discharge moves from a cathode in one set to a cathodein the other set, the positive puise applied to the grid ofthenon-conducting tube. will cause the circuit to shift to the other stablecondition.

Each plate in the second iiip-iiop circuit 10G is connected respectivelyto differentiating and negative clipping circuits 142 and 144 which arearranged to act as an.OR circuit 106. Each of these circuits 142 and 144includes. a load resistor 1'46 so that when the plate voltage of eithertube in the tiip-iiop circuit 106 increases, there will be a positivevpulse across the resistor 146. Since this resistor 146 is connected to agrid 14S in the gate 110 through the AND circuit, it will raise thepotential thereof to a more positive level for a short time. It may thusbe seen that there will be no positive pulse on the resistor146'unlessan event is completed and that such a pulse will be anunambiguous indication of the completion of an event irrespective of'the sense ofthe event which occurred.

The grid 148 of the gate tube 132 is also connected to an AND circuit166 that includes diodes 157 and y153 and the resistor 15S. The ANDcircuit is also connected with capacitor 15?, resistor 152 connected to.junction 1511 and diode 154'. The AND circuit 10S isV connectedA to thesecond plate 82' in the rst squaring`v circuit 62 so that. it willreceive the square wave pulse occurring when the discharge settles oncathode K0. This will result in a positive pulse combining with any.positive pulses that occur in the OR circuit 166. if the two pulsesoccur simultaneously, the resultant pulse. wili be of sufcient amplitudeto cause a'positive pulse to occur in the. output 156 of the gate 110 ifit was open at theA time the pulses occur.

1n order toregister a positive count, it is essential that threeconditions exist: (l) No negative countswere stored prior to thecommencement of the event; (2') the event must be completed, and' (3)the completed event occurred ina positive sense. When the dischargesettles on cathode K0, there. will' be no negative counts stored whenthe event isv completed. Consequently, whenever the discharge leavescathode K0, there will' have been no counts stored at the beginningofthe event. Thus, the firstv condition will be unambiguously indicated bythe voltage across the resistor 42 dropping to zero. This voltage drop'willy result in the bias on the input grid l74 of the squaring circuit62 being removed, a drop of the voltage on the differentiatingandpositive clipper circuit 1.23, a negative pulse on the grid of thefirst tube 112 in the Hip-flop circuit 94, cut offl of the tirst tube112 and conduction of the second tube 114 if this condition did" Thecontrol grid of the. second tube is connected to the plate of the inputtube.

not previously exist, an increase in the potential of the plate 118 anda corresponding positive increase in the potential on the control grid134 so as to permit the tube 132 to conduct and thereby open the gate110 so that any signals may be passed to the counter 30.

When the discharge in the second discharge tube 48 transfers from acathode in one set to a cathode in the other set, a complete event hasoccurred. Thus the second condition will be indicated by the potentialsacross the resistors 54 and 56 reversing. This voltage change willresult in the conduction in the squaring circuits 66 and 63 reversing, anegative pulse being applied to grid of one of the tubes in the flip-dopcircuit 100 so as to change the status thereof from one stable conditionto the other, a positive pulse appearing across the resistor 146 and apositive pulse flowing to the grid 148 of the gate 110 providing the ANDcircuit has received a pulse from grid 82 of tube 72.

When the discharge arrives at the cathode K0, it must have moved fromthe cathode K1 or have returned to KD after leaving the same and movingin a positive direction across the adjacent guide pins. Either of theseconditions necessitates a positive event. Thus the third condition willbe indicated by the voltage across resistor 42 increasing. This voltageincrease will result in the lirst tube 70 in the squaring circuit 62becoming conductive and the second tube 72 becoming non-conductive. Thiswill cause a voltage to be applied to the AND circuit and if anothervoltage pulse is applied to the AND circuit from the OR circuit, anattempt will be made to gate the tube 132 on.

It will be apparent from the foregoing that during the time that thedischarge is on the cathode K1 the gate 132 will be closed. It also willbe apparent that when the discharge leaves cathode K the gate 132 willopen. With the gate open it couples the AND circuit signal to the outputterminal providing a signal has been produced by the OR circuitindicative of a completed event.

The circuiting of this invention is thus such that the counter will onlybe actuated when the discharge is transferrcd from cathode K1, to theguide pins and back to K0 providing there is a completed event. If thedischarge is transferred in a negative direction from cathode K0 tocathode K1 the gate will be closed when the discharge settles on K1 toprevent actuation of the counter. When the discharge is beingtransferred between the cathodes other than K0 and K1 the gate 132remains closed so that the counter is not actuated.

It is intended now to describe the operation of this counting circuit asthe discharge is transferred between cathodes in the negative storagecounting tube 36. Assume rst that the discharge is on cathode K0 andthat the discharge will be transferred to cathode K1 by proper signalsfrom source 22. This event is in a negative direction so that thecounter 30 will not be actuated. In addition when the discharge istransferred to cathode K1 `at the end of the cycle one negative countwill be stored.

As the discharge leaves cathode K0, the voltage will decrease that wasdeveloped across resistor 42 which will correspond to the trailing edgeof a square wave voltage that was started when conduction began on K0.The pulse of voltage developed across resistor 42 causes squaringcircuit 62 to develop a positive pulse of voltage which decreases as thedischarge leaves K0 and causes a negative pulse to be applied to grid126 of tube 112 through circuit 128. This negative pulse coincides intime with the decrease in voltage across resistor 42 and drives tube 118non-conductive and tube 114 conductive. Flip-dop 94 has an output andattempts to open gate tube 132. It thus can be seen that thetransferring of the discharge from cathode K0 has attempted to open thegate tube 132. This transferring of conduction from cathode K1,satisties condition one noted above but there are two other conditionsto fulfill if the counter 30 is to be actuated.

' The third condition noted above will not be fulfilled since the countis in a negative direction. Thus, as the discharge left K0 and thevoltage decreased across resistor 42, there is no output from squaringcircuit 62 to one side of diode 157 and the gate 132 therefore cannotremain open since the AND circuit will not permit this. The countertherefore cannot be actuated even though the rst condition for actuationis met.

When the pulse transfers to cathode K1, a voltage is developed acrossresistor 44. This causes a negative pulse to be delivered to the grid oftube 114 through the action of squaring circuit 64 and circuit 130. Tube114 is now driven non-conductive and tube 112 conductive. The arrival ofthe discharge on cathode K1 will thus re duce the output of flip-Hop 94so that it no longer biases the gate tube 132 to a conductive condition.

The second condition noted above, that being that a completed event hasoccurred, will be met by the transfer of discharge to K1 since thedischarge will shift in tube 48 and through squaring circuits 66 and 68and llipilop 10() will cause a positive voltage one side of diode 153 ofthe AND circuit.

1n summary, it can be seen that during the transfer of discharge fromcathode Ko to K1 the first and second conditions noted above that arerequired for counting were met but since the third condition was notmet, the counter 30 is not actuated.

lf it is assumed now that the discharge is transferred from cathode K1back to cathode K0, the counter 30 will not be actuated since eventhough the event is now in -a positive direction, one negative count isnow being stored. In such a transfer, conditions two and three will bemet but condition one which requires that no negative counts were storedprior to the commencement of the event will not be met.

As the discharge leaves cathode K1, the voltage across resistor 44 dropsto zero. This Will not effect the flipflop circuit 94 since no negativepulse will be passed to it. As the discharge arrives at cathode K0, avoltage is developed across resistor 42. This voltage will cause anoutput from squaring circuit 62 to diode 157 to attempt to turn on gatetube 132 but causes no negative pulse on the grid of tube 112 to driveit non-conductive. Since an event has been completed, a pulse is appliedto diode 153 to also attempt to drive tube 132 on. The AND circuit nowwill drive grid 148 positive but since there is no output from ip-flop94 to grid 134, the counter 30 is not actuated. If the discharge nowtransfers from cathode K0 to a guide pin and back to cathode K0, thecounter 30 will be actuated by one count since all three conditions forcounting are met. As the discharge leaves K0, the drop in voltage acrossresistor 42 results in a negative pulse being applied to grid 126 oftube 112 due to squaring circuit 62 and circuit 128. Tube 112 ifconductive is driven non-conductive and if non-conductive, remainsnonconductive. With tube 112 non-conductive, grid 134 of gate tube 132is biased to cause tube 132 to conduct. When the discharge returns tocathode K11, the iiip-op circuit 94 is not effected so that tube 112remains non-conductive and grid 134 remains biased positive. Since anevent is completed by transfer of glow in tube 48, a positive voltageappears at one side of diode 153 as the discharge returns to K0. Apositive.

voltage also now appears at one side of diode 157 since the voltage riseon resistor 42 will cause this by the output from squaring circuit 62.The AND circuit now causes grid 148 to go positive and since grid 134 ispositive, the counter 30 is actuated.

It can be seen that transfer' of discharge from cathode K1 to cathode K2will only store negative events since only the third condition forcounting is met. The same is true for transfers of discharge beyondcathode K2 in the negative direction.

It is to be understood that, although the invention has been describedwith specific reference to a particular embodiment thereof, it is not tobe so limited since changes andlalterations thereinmay, be made4 whichare within the full? intended scope of t-his invention as defined by theappended' claims.

We claim:

l. A net positive digital counter comprising, a storage circuit forstoring a plurality of counts corresponding to the, number of. events ofone sensewhich. have occurred, means including a multicathodedischargetube responsive to the completion' of^an'event, and countingmeans separate from said storage circuit for indicating a count onlywhen an event of an opposite sense is completed and there are no countspreviously stored in said storage circuit prior to the commencement ofthe event.

2. In a device of the class described, the combination comprising, meansfor producing 4a series of signals indicative of the occurrence of thefirst and second events of opposite sense, a first multicathode gaseousdischarge tube connected with said means for storing events of saidfirst sense, means including a second multicathode gaseous dischargetube connected with said first means and responsive to the completion ofan event, and counter means connected with said discharge tubesefiective to count an event of said second sense Whenever such an eventis completed and there are no counts of said first sense stored in firstdischarge tube.

3. l'n a device of the class described, the combination comprising,means for producing a series of signals indicative of the occurrence ofpositive and negative events, a first multicathode gaseous dischargetube connected With said means for storing negative events, first andsecond resistors connected in the cathode circuits of adjacent cathodesof said tube, a second multieathode gaseous ldischarge tube connectedwith said means having adjacent pairs of cathodes connected withdifferent output circuits, a gate circuit, a counter connected torespond to the output of said gate circuit, means connected with saidgate circuit and with said first and second resistors for controllingthe conduction of said gate circuit as a function of the voltagesappearing across said resistors, and means connecting the outputcircuits of said second multicathode discharge tube with said gatecircuit.

4. In a system of the class described, the combination comprising, firstmeans for producing a series of signals indicative of the sense andnumber of a series of events, a multicathode discharge tube connectedwith said first means, counting means, and means for actuating saidcounting means in response to the discharge on a cathode of saidmulticathode discharge tube leaving said cathode and then returning tosaid same cathode during the application of a signal applied to saidtube which is indicative of the occurrence of only one event.

5. In -a system of the class described, the combination comprising,first means for producing a series of signals indicative of the senseand number of a series of events, a multicathode discharge tube to beconnected with said first means having a first cathode disconnected fromany power source whereby the discharge in said tube cannot betransferred to said first cathode, means connected with a second cathodeand located adjacent said first cathode for developing a controlvoltage, a gate circuit, and means for controlling said gate circuit inaccordance with said control voltage.

6. In a counting system, the combination comprising, a source ofinformation, a multicathode discharge tube connected with said source ofinformation, the character of the information from said source beingsuch that a discharge can be transferred from cathode to cathode in saidtube in either direction, said tube being connected such that with thedischarge on a predetermined cathode the input information causes thedischarge to leave said cathode and then immediately return to saidcathode, and counting means operated in response to the Ileaving l@ ofthe discharge, from said-cathode and the immediately subsequentreturning of the discharge to said cathode during the application of asignal to said tube Which is indicative of theoccurrenceofV only oneevent:

7i A counting-systemcomprising, a gate circuit having a pair'of-Ycontrol' electrodes, a source'of information indicative of a seriesofevents-of different sense, storage means for storingevents'ofone-sense connected with said` source of'information, means for applyinga' signal to one of the electrodes of said gate circuit when saidstorage means is storing no counts of said one sense, an AND circuithaving a pair of inputs and an output connected with the other of saidgate electrodes, means for causing a signal to be applied to one of theinputs of said AND circuit when an event has been completed in eithersense, and meansy for at times causing a signal to be applied to theother input terminal of said AND circuit as a result of `the eventoccurring in a predetermined sense.

8. A counting system comprising, means for producing signals indicativeof the number and sense of a series of events, storage means for storingcounts of one sense, a counter means for producing a first signalvoltage when there are no counts stored in said storage means, meansseparate from said storage means for producing a second signal voltagewhen an event has been completed, means for producing a third signalvoltage when the event Ioccurs in a direction opposite to that that canbe stored by said storage means, and means for actuating said counterwhen said first, second and third signal voltage are occurringsimultaneously.

9. A counting system comprising, means having an output providingsignals indicative of the number and sense of a series of events,storage means connected with said first means for storing counts of onesense, means indicating a first condition that there are no eventsstored in said storage means at the beginning of an event, meansindicating a second condition that the event occurred in a senseopposite to the sense of counts that can be stored by said storagemeans, means separate from said storage means indicating a thirdcondition that the event was a completed event, a counter, and meansconnecting said counter and indicating means whereby said counter isactuated only when said first, second and third conditions arefulfilled.

10. In a counting system of the type described, the combinationcomprising, a multicathode discharge tube, means feeding inputinformation to said tube consisting of the number and sense of a seriesof events, a first resistor connected with a first cathode of said tube,a second resistor connected with a second cathode of said tube that islocated adjacent said first cathode, first and second squaring circuitsa flip-flop circuit having an output terminal and a pair of inputterminals connected in circuit respectively with said first and secondresistors through said first and second squaring circuits, a gatecircuit connected with the output terminal of said flipfiop circuit, anda counter connected with said gate circuit.

ll. In a device of the class described, the combination comprising, apick-up responsive to a series of events for producing signalsindicative of the number and sense of said events, a multieathodedischarge tube for storing a number corresponding to the occurrence ofthe events of one sense, means separate from said multicathode dischargetube and connected with said pick-up responsive to the completion of anevent of either sense, and means for counting the completion of eventsof an opposite sense that occur only when said multicathode dischargetube does not have a count stored therein of said one sense and onlywhen an event is completed.

(References on following page) References Cited in the le of this patentUNITED STATES PATENTS Beman et a1 July 27, 1954 Pudelko et al. Feb. 19,1957 Wood Apr. ,23, 1957 Applegate Apr. 23, 1957 Peacock Apr. 1, 1958Hayes et al May 6, 1958 12 Gordberg Ian. 12, 1960 Rosenberg Dec, 13,1960 Chao Dec. 27, 1960 Irvine et a1. Mar. 14, 1961 FOREIGN PATENTSGreat Britain Ian. 23, 1957 Great Britain Nov. 13, 1957

1. A NET POSITIVE DIGITAL COUNTER COMPRISING, A STORAGE CIRCUIT FORSTORING A PLURALITY OF COUNTS CORRESPONDING TO THE NUMBER OF EVENTS OFONE SENSE WHICH HAVE OCCURRED, MEANS INCLUDING A MULTICATHODE DISCHARGETUBE RESPONSIVE TO THE COMPLETION OF AN EVENT, AND COUNTING MEANSSEPARATE FROM SAID STORAGE CIRCUIT FOR INDICATING A COUNT ONLY WHEN ANEVENT OF AN OPPOSITE SENSE IS COMPLETED AND THERE ARE NO COUNTSPREVIOUSLY STORED IN SAID STORAGE CIRCUIT PRIOR TO THE COMMENCEMENT OFTHE EVENT.